A mud hole-plagued track built in a "hell of a hurry" and signalling issues may have been factors in the Sydney to Melbourne train derailment, according to an expert.
Two people were killed on Thursday when an XPT diesel locomotive and five carriages came off the tracks near Wallan Station, 45km north of Melbourne.
An ACT male driver, 54, and a regional Victorian train pilot, 49, died and several passengers were injured.
Rail Futures Institute president John Hearsch told AAP on Friday the line between Junee and Melbourne was known for its "mud holes" which left the track floating in mud.
"It is not properly supported. This is quite frequent along the track and we have had a bit of rain lately and they tend to get worse," Mr Hearsch said.
An upgrade is under way for the entire North East Line between NSW and Victoria, which has been allocated $235 million in federal funding. The works are due to finish next year.
Mr Hearsch said the track should be replaced.
"It was built in a hell of a hurry. It is fair to say we have had some trouble ever since," he said.
The double-track at Wallan, which allows trains to pass, is managed by a signalling system. But Mr Hearsch said this was not working due to a fire at Wallan's signal hut in January.
"That signal has been out of action because of that fire. It has really put the signalling out of action between Donnybrook and Kilmore East," Mr Hearsch said.
Instead of normal signalling, a person who knows the track section rides with the driver while radio contact is kept with the controller in NSW, the train expert said.
The federal government-owned Australian Rail Track Corporation operates the track and is understood to be responsible for the signalling.
"We are providing full support to the investigation which will look at all potential factors," the ARTC statement to AAP reads.
Deputy Prime Minister Michael McCormack stressed multiple times on Friday that no authority - state or federal - would let a train run on unsafe track.
"That just wouldn't happen," he said at the site.
Transport for NSW operates the trains on this track. NSW Regional Transport Minister Paul Toole wasn't aware of concerns about the track's condition.
Rail Train and Bus Union Victorian Secretary Luba Grigorovitch said V/Line drivers had "refused to traverse this section over the past week".
V/Line declined to comment.
Train services on the Albury line resumed on February 10 after an incident with a V/Line passenger train and a derailed freight train near Barnawartha in late January.
In December, Infrastructure Australia said the business case for an upgrade of the Melbourne-Albury North East Rail Line "should not be included on its priority list".
The ATSB will give a preliminary report in a month before a final version in 18 months.
Australian Associated Press
